Around this time, right as he was ramping up at Microsoft, Nadella married his wife, Anu, who still lived in India. Then, things got complicated, thanks to immigration law. Nadella even gave up his permanent resident status and took an H-1B visa to exploit a loophole that could bring Anu to America to live with him. (He got his citizenship later.)

During his first years at Microsoft, Nadella also impressed his coworkers and managers alike by commuting every weekend from Microsoft's campus in Redmond, Washington, all the way to the University of Chicago's Booth School of Business to finish his MBA. He'd finally graduate in 1997.

In 2001, Nadella rose to corporate VP of Microsoft Business Solutions. The group had been formed through a series of acquisitions, including Great Plains, which made accounting software for small and midsize businesses. The group was also building a cloud-based CRM system to compete with Salesforce. Eventually all these products would be rebranded as "Dynamics."

Nadella's star just kept rising: By 2007, Nadella was senior VP of Microsoft Online Services, which meant that he was in command of the Bing search engine, as well as early online versions of Microsoft Office and the Xbox Live gaming service.

In February 2011, Nadella would get another promotion, this time to president of the Server and Tools Division. At the time, that group oversaw cash-cow products for companies' data centers, like Windows Server and the SQL Server database. But it also hosted one of Ballmer's boldest gambles, the Microsoft Azure cloud platform.

By this point, Microsoft was running into trouble. On the PC side, Windows 8 was a disaster, the iPhone and Android were outrunning Windows phones by leaps and bounds, and Bing just couldn't make a dent in Google's search dominance. And Ballmer took the heat.

Nadella sent an email to employees when he first took the job.

"I am 46. I've been married for 22 years and we have 3 kids. And like anyone else, a lot of what I do and how I think has been shaped by my family and my overall life experiences. Many who know me say I am also defined by my curiosity and thirst for learning. I buy more books than I can finish. I sign up for more online courses than I can complete. I fundamentally believe that if you are not learning new things, you stop doing great and useful things. So family, curiosity and hunger for knowledge all define me. "

Nadella has also compared programming code to poetry.

"You're trying to take something that can be described in many, many sentences and pages of prose, but you can convert it into a couple lines of poetry and you still get the essence, so it's that compression. The best code is poetry," he said to Politico.

Nadella's whole philosophy is about partnering and making sure that Microsoft software and services are available wherever customers are — even if that's not Windows. That's why his first big hire was ex-Qualcomm exec Peggy Johnson, now Microsoft VP of business development, to help partner up with outside companies.

So, yeah. Nadella's been busy. But investors love it: From 2014 to 2015, his first year, Microsoft stock jumped 14%. Today, in 2018, Microsoft's stock price has almost tripled from when he first took the reigns.

Employees love him, too, with many fond of his leadership style, which emphasizes learning and making mistakes as a hedge against overconfidence and arrogance. Executives credit his leadership with helping Microsoft refocus on what it's good at.

As we go into 2019, Nadella still has plenty of challenges to tackle. Shrinking PC sales are hampering Microsoft's Windows 10 ambitions, while it's struggled to make its Cortana personal assistant a mass-market success. And the Xbox One video-game console is struggling against the competing Sony PlayStation 4.

But for the first time in a long time, things are looking up for Microsoft. Recently, Microsoft became the most valuable company in the world, overtaking Apple for the first time since 2010. Whether or not it stays that way, it's clear that Microsoft is on the upswing.

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